The present invention generally relates to thermal inkjet printing systems, and more particularly to a thermal inkjet cartridge system having means therein for automatically applying a printhead cleaning solution to the cartridge printhead.
Substantial developments have been made in the field of electronic printing technology. Specifically, a wide variety of highly efficient printing systems currently exist which are capable of dispensing ink in a rapid and accurate manner. Thermal inkjet systems are especially popular in this regard. Thermal inkjet systems basically include an ink reservoir in fluid communication with a substrate having a plurality of resistors thereon Selective activation of the resistors causes thermal excitation of the ink and expulsion thereof from the ink cartridge. Representative thermal inkjet systems are discussed in U.S. Pat. No. 4,500,895 to Buck et al.; U.S. Pat. No. 4,794,409 to Cowger et al.; the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985); and the Hewlett-Packard Journal, Vol. 39, No. 4 (August 1988), all of which are incorporated herein by reference.
In general, thermal inkjet printing cartridges use a variety of functional components, all of which must cooperate in a precise manner to achieve maximum printing efficiency. One important component involves an orifice plate having a plurality of openings therein. Ink is ejected through these openings during cartridge operation. To ensure proper cartridge operation, the orifice plate and openings must be kept clean and free of debris at all times. Otherwise, a wide variety of problems can occur which impair printer performance For example, debris on the orifice plate surface (e.g. from stray paper fibers and the like) can reduce the quality/resolution of printed images. Similar problems can occur with respect to dried ink which may form crusts on the orifice plate during cartridge operation. Such crusts typically result from evaporation/oxidation of the ink being ejected from the cartridge.
In order minimize the foregoing problems, devices known as "service stations" have been created which are physically mounted to and within the main printer unit. They are specifically oriented within the printer unit so that when the cartridge is not operating and is in a "parked" position, the cartridge is directly over and above the service station Service stations have a variety of components which are designed to serve many purposes These purposes include but are not limited to (a) priming the printhead; (b) covering the orifice plate and openings therein when the printhead is not in operation; (c) wiping contaminants from the orifice plate; (d) preventing ink from drying out in the openings of the orifice plate; and (e) providing a location to eject soft, viscous plugs of ink which may form in the openings of the orifice plate. Specific systems designed to perform some or all of these functions are disclosed in U.S. Pat. No. 4,853,717 and U.S. Pat. No. 5,027,134 which are incorporated herein by reference.
One of the most important functions of a service station is item (c) above which involves wiping contaminants from the orifice plate and openings therein. To accomplish this, U.S. Pat. No. 4,853,717 discloses the use of a resilient elastomeric wiper member having a blade portion which comes in contact with the printhead during operation thereof. More specifically, as the cartridge moves in a reciprocating manner within the printer unit, the blade portion of the wiper member brushes against the printhead to enable the cleaning thereof.
Another type of wiper system is disclosed in German Patent Specification 3,817,754 which apparently involves an external pad soaked with cleaning agents mounted to an external, rotating arm. As the rotating arm moves, the pad positioned on the arm wipes against the printhead components of the cartridge.
Notwithstanding the systems described above, a need remains for a printhead cleaning system of superior efficiency which not only provides a wiping unit, but also allows the controlled delivery of a printhead cleaning solution to the printhead. This enables the wiping unit to more efficiently remove dried ink materials and the like. Accordingly, the present invention satisfies this need in a unique and highly effective manner as described herein below.